>Won't many of the projects in the Ubuntu repositories be unavailable because of architectural reasons, i.e. ARM phones versus x86/64 desktops?
Almost the entirety of Linux userland software is very portable because the server space needs it to run on x86/sparc/power/itanic/whatever. There are exceptions but they tend to be rare and temporary, because hardware vendors don't want customers switching to x86 just because foo app doesn't run on their architecture, and for open source apps the hardware vendors can fix it themselves.
Meanwhile Linux is about the only sensible thing you can currently install on the vast expanse of old PowerPC Macs that can't run current versions of MacOS but can run current versions of Ubuntu or Debian, so any that get recycled into a personal server or a DVR box or whatever will have users pointing out any problems and requesting they be fixed.
And for the most part portability is portability: If you find x86 assembly somewhere and replace it with portable C and an ifdef to use the asm only on x86, or fix an endian issue, you haven't just fixed it for PowerPC or SPARC, you've fixed it for everyone.
This, incidentally, is why having a single architecture is so unhealthy: It promotes everyone forgetting about portability entirely, which prevents new, better architectures from taking hold merely because it's so much more work to port the existing installed base of software.
I run Raspbian, another Debian-based distro, on my Raspberry Pi (ARMv6 CPU) and haven't run into any missing packages yet. Can't imagine there are many projects out there these days that are still architecture-specific, outside of compilers and JITs and so forth, many of which (e.g. LuaJIT, V8, LLVM) already support ARM.
As an example, Yesod doesn't work on the raspberry pi, because GHCi is not in the debian ARM repositories. This is annoying, because compiling everything yourself takes forever on the raspberry.
It should be noted there is a difference between "not in repos, so I have to manually build, but it works" and "there is absolutely no way to run this software on this platform due to the processor".
It is really promising for the current software written against glibc and friends to have all these arm devices running homebrew ARM builds without many hitches.
Especially compared to a platform like, say, Windows, where even though there is an ARM version (Windows RT) which is extremely stripped down and awful on all fronts, there is no software for it because of API compatibility issues and the fact that without open source recompiling most of the Windows software catalog is impossible.
Ah, interesting, had actually looked into GHC and knew there was no GHCi support for ARM (also, ARM is only a Tier 2 platform), but did not realize that made it impractical to use Yesod. That kinda sucks.
Much of the software in Ubuntu is available on ARM today. If you have an Ubuntu ARM device (say, you are running the desktop on a Panda board), you can launch Ubuntu Software Centre and see for yourself.
For a less pretty view (and one that will only make much sense if you already understand how the Ubuntu archives are organized (poorly)), check out http://ports.ubuntu.com/
